I have data like this:
[
{
"category":"Fruits",
"name":"Apple"
},
{
"category":"Fruits",
"name":"Manggo"
},
{
"category":"Vegetables",
"name":"Water Spinach"
}
]
I want to grouping by java 8, I've tried with :
Map<String, List<MyData>> myData
= list.stream().collect(Collectors.groupingBy(d -> d.getCategory()));
But the result is not what I need. Because the result I expected was Fruits = 2, Vegetables = 1
Based on the result you're after, you'll need to use a groupingBy() collector together with a counting() collector:
Map<String, Long> soldCopiesStats = list
.stream()
.collect(Collectors.groupingBy(MyData::getCategory, Collectors.counting()));
You can use Collectors.counting as the downstream collector of groupingBy to get the count in each group.
Map<String, Long> myData = list.stream()
.collect(Collectors.groupingBy(d -> d.getCategory(), Collectors.counting()));
